Air conditioner

ABSTRACT

An air conditioner comprises an evaporator for transferring heat from air to a refrigerant gas, a temperature sensor for sensing a temperature associated with the evaporator, a compressor for compressing the refrigerant gas, an electric motor for driving the compressor, and a controller for controlling the speed of the motor, wherein the controller is responsive to the temperature sensor.

FIELD OF THE INVENTION

The present invention relates generally to air conditioning and in particular, to air conditioners.

Although the invention will be described with particular reference to an air conditioner for a boat, it will be appreciated that the air conditioner according to the present invention is not limited to use on a boat. For example, the air conditioner may be used for air conditioning a truck cabin, the interior of a racing car, a crane cabin, or the interior of a house.

BRIEF DISCUSSION OF THE PRIOR ART

Most air conditioners need to be powered by an AC electrical power supply such as a mains electrical power supply. However, such air conditioners are not suitable for use on boats, racing cars, crane cabins or remote housing where mains power is not available.

Car air conditioners are known which have a particular type of compressor called a “scroll” compressor. The scroll compressor is normally coupled to an engine drive shaft of the car which the air conditioner is installed on so that the compressor is driven directly by the engine. The disadvantage of using the car engine to drive the air conditioner compressor is that doing so reduces the performance of the car because some of the power which is produced by the engine is diverted from rotating the wheels of the car to driving the compressor. While this is normally acceptable for ordinary cars, it is normally not acceptable for racing cars.

Air conditioners which are powered by a DC electrical power supply are known. Such air conditioners are able to run off a battery and typically include a scroll compressor, a DC electric motor, a thermal expansion valve and an evaporator which are connected together in a particular way. However, these types of air-conditioners typically draw an enormous amount of electrical current (typically over 100 A) which means that if they are powered by a battery, the battery will usually run out of charge very quickly. This is one of the reasons why the air conditioner of a typical car cannot operate when the engine of the car is not running.

The operation of many DC powered air conditioners is controlled by a thermostat which is located in the air conditioner's evaporator core. The thermostat normally controls the motor which drives the compressor of the air conditioner so that the temperature of the evaporator core is kept at around 3° C.-5° C. This normally means that the thermostat repeatedly turns the motor on and off to maintain the evaporator core at the required temperature. A problem with this is that when the motor is turned on, it is normally run at its maximum speed so that it consumes a lot of power. This is not desirable if the air conditioner is being powered by a battery.

It would therefore be desirable to provide an air conditioner which is able to be powered by a DC electrical power supply and which is able to consume less power than known DC powered air conditioners.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome, or at least ameliorate, one or more of the deficiencies of the prior art mentioned above, or to provide the consumer with a useful or commercial choice.

Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying illustrations, wherein, by way of illustration and example, a preferred embodiment of the present invention is disclosed.

According to a broad aspect of the present invention there is provided an air conditioner comprising an evaporator for transferring heat from air to a refrigerant gas, a temperature sensor for sensing a temperature associated with the evaporator, a compressor for compressing the refrigerant gas, an electric motor for driving the compressor, and a controller for controlling the speed of the motor, wherein the controller is responsive to the temperature sensor.

By controlling the speed of the motor in an appropriate manner, the amount of electricity consumed by the air conditioner can be significantly reduced so that it is feasible to use a battery to power the air conditioner.

Although any suitable type of evaporator may be used, it is preferred that a core of the evaporator includes a plurality of parallel tubes through which the refrigerant flows, and a plurality of fins which surround the tubes such that air is able to flow through the evaporator and past the tubes.

It is preferred that the evaporator core is a one-piece core.

Preferably, the evaporator is a 1.5 tonne/18,000 BTU evaporator.

The evaporator core may be mounted inside a housing which is fabricated from a non-corroding material. For example, the evaporator core may be mounted inside a housing which is fabricated from fibreglass.

The air conditioner preferably includes a fan for drawing air through the evaporator core. The fan may be a barrel-type fan.

The air conditioner preferably includes a vent from which air which has been cooled by the evaporator is output.

Although the air conditioner may use any suitable type of refrigerant gas, it is preferred that the air conditioner uses 134 A gas which is the industry standard gas for automotive air conditioners.

The temperature sensor may be of any suitable type. However, it is preferred that the temperature sensor is a thermistor.

The temperature sensor preferably senses the temperature of the evaporator core.

The compressor is preferably a scroll compressor. It is particularly preferred that the compressor is a scroll compressor of the type which is commonly used in automotive air-conditioning applications.

The electric motor is preferably a brushless DC electric motor. Brushless DC electric motors normally have fewer moving parts compared to other types of DC motors. Consequently, the friction losses of brushless DC motors are typically less than the friction losses of other types of DC motors. Reducing the friction losses of the electric motor is advantageous because it helps to improve the efficiency of the air conditioner by reducing the amount of electricity which the air conditioner consumes.

The electric motor is preferably adapted for soft starting and soft stopping. Soft starting the electric motor prevents the motor from being subjected to high surge currents at start-up, and soft stopping prevents the motor from being subjected to harsh stop currents which can occur in an electric motor as a result of the back emf which is produced when power to the motor is abruptly disconnected. Soft starting and soft stopping the electric motor also reduces wear and tear on drive components such as gears, pulleys and belts which may be employed so that the electric motor can drive the compressor.

The electric motor preferably has multiple phases. In a particular preferred form, the electric motor has three phases.

It is preferred that the air conditioner also has at least one position sensor for sensing the position of an armature of the motor. Each position sensor preferably outputs an electric pulse when sensing the position of the armature. Each position sensor is preferably housed in the rear of the motor.

Preferably, the controller has a plurality of phase outputs, wherein each phase output is connected to a respective phase of the motor. The controller preferably activates the phase outputs in response to the position sensors such that the armature of the motor rotates. The controller may be configured for soft starting or soft stopping of the electric motor.

The electric motor is preferably a permanent magnet electric motor. Permanent magnet electric motors typically consume less electricity than other types of electric motors because electricity is not required to establish the magnetic filed in the motor.

Preferably, an armature of the motor has skewed-type magnets which are configured to prevent the motor from cogging. Cogging is a term which is used to describe the growling noise which conventional electric motors sometimes make when starting or when running at a slow speed.

The electric motor may be adapted to operate from any suitable supply voltage. However, it is preferred that the electric motor is adapted to operate from a supply voltage in the range of 12V-48V.

In a particular preferred form, the electric motor is a 750 W 24V DC electric motor.

In a particular preferred embodiment, the electric motor has a maximum speed of 2,000-2,200 rpm.

The magnetic fields in the electric motor are preferably situated around an armature of the motor and on the inside of a housing of the motor so as to provide better transfer of heat to the housing which may function as a heat sink.

It is preferred that the electric motor has a housing which is fabricated from aluminium.

Preferably, the air conditioner also includes a toothed pulley mounted on a drive shaft of the motor, a toothed pulley mounted on a drive shaft of the compressor, and a toothed drive belt trained around the pulleys such that the teeth of the drive belt mesh with the teeth of the pulleys. It has been found that coupling the drive shaft of the motor and the drive shaft of the compressor together in this manner inhibits slippage between the drive belt and the pulleys when the motor is being started and stopped. Inhibiting slippage between the drive belt and the pulleys reduces the amount of energy which is wasted by the air conditioner when the motor drives the compressor.

The controller preferably includes a circuit board, at least one heat sink, a cover, and a cooling fan.

Preferably, the controller controls the speed of the motor to maintain the temperature of the evaporator at a predefined temperature or within a predefined range of temperatures. It is preferred that the controller incrementally increases or decreases the speed of the motor if the temperature of the evaporator is not equal to the predefined temperature or does not fall within the predefined range of temperatures. In a particular preferred embodiment, the controller controls the speed of the motor to maintain the temperature of the evaporator core at a temperature of 3° C.-5° C.

Preferably, if the heat load on the evaporator is too high, the controller increases the speed of the motor to a maximum speed until the heat load on the evaporator is reduced by a sufficient amount. The controller then decreases the speed of the motor so as to reduce the amount of electrical power which is consumed by the motor and hence the air conditioner.

Preferably, the air conditioner also includes a temperature sensor for sensing the temperature of the room or other space which is cooled by the air conditioner. The air conditioner preferably turns off when the temperature in the space reaches a predetermined room temperature, and turns on when the temperature in the space exceeds the predetermined room temperature by a minimum amount. This cyclical mode of operation helps to reduce the amount of electricity which is consumed by the air conditioner.

Preferably, the air conditioner also has a user control panel for allowing a user to control the air conditioner.

The air conditioner may also include an interface module for interfacing a DC power source with the controller. The interface module preferably also interfaces the DC power source with a user control panel, and interfaces the user control panel with the controller.

The air conditioner may be powered by any suitable DC voltage source. Preferably, the air conditioner is powered by a battery.

The air conditioner may be adapted to be powered at any suitable DC supply voltage. Preferably, the air conditioner is adapted to be powered by a DC voltage supply in the range 12V-50V.

The air conditioner preferably includes a thermal expansion valve for the refrigerant gas. The thermal expansion valve is preferably a changeable orifice thermal expansion valve. In a particular preferred form, the valve has an orifice which gives the valve a capacity of approximately 4 kW.

Preferably, the air conditioner also has a heat exchanger for cooling the refrigerant gas. The heat exchanger is preferably a water-cooled heat exchanger. If the air conditioner is installed on a boat, it is preferred that the heat exchanger is a seawater-cooled heat exchanger.

If the air conditioner includes a water-cooled heat exchanger, it is preferred that the air conditioner also includes a water pump for pumping water through the heat exchanger. If the air conditioner is installed on a boat, the water pump is preferably mounted below the waterline of the boat.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying illustrations, in which:

FIG. 1 is a schematic block diagram of a portion of an air conditioner;

FIG. 2 is a first perspective view of the air conditioner;

FIG. 3 is a second perspective view of the air conditioner;

FIG. 4 depicts the air conditioner with the motor, compressor and controller thereof exposed;

FIG. 5 depicts the motor, compressor and controller of the air conditioner;

FIG. 6 depicts the controller of the air conditioner with a cover and fan of the controller partially removed;

FIG. 7 depicts the belt and pulleys of the air conditioner;

FIG. 8 depicts the heat exchanger of the air conditioner; and

FIG. 9 depicts the user control panel of the air conditioner.

DETAILED DESCRIPTION OF THE ILLUSTRATIONS

A schematic block diagram of an air conditioner 20 for air conditioning the cabin of a boat is depicted in FIG. 1. The air conditioner 20 comprises a temperature sensor 21 which is in the form of a thermistor. The temperature sensor 21 senses the temperature of an evaporator core of the air conditioner 20.

A controller 22 which is responsive to the temperature sensor 21 controls the speed of a three-phase brushless 750 W 24V DC electric motor 23 which has a maximum speed of 2200 rpm. The motor 23 has a drive shaft 24. A toothed pulley 25 is mounted on the drive shaft 24 such that the pulley 25 rotates with the shaft 24.

The air conditioner 20 also includes a scroll compressor 26 which includes a drive shaft 27. A toothed pulley 28 is mounted on the drive shaft 27 such that the pulley 28 rotates with the shaft 27. A drive belt is trained around the pulleys 25, 28 so that the motor 23 is able to drive the compressor 26.

The drive ratio of the pulley 25 to the pulley 28 is 3 to 1.

An interface module 29 connects a 12-48V battery 30 to a user control panel 31 and to the controller 22 so that the battery 30 is able to supply electrical power to the control panel 31 and to the controller 22. The control panel 31 allows a user to control the room temperature which is produced by the air conditioner 20.

The air conditioner 20 utilises energy efficient evaporator temperature feedback to maintain the evaporator core at a temperature of 3° C.-5° C. In particular, the controller 22 incrementally increases or incrementally decreases the speed of the compressor 26 by incrementally increasing or incrementally decreasing the speed of the motor 23 if the evaporator core temperature falls outside of the aforementioned temperature range. If the evaporator core temperature is below 3° C.-5° C., the controller 22 incrementally decreases the speed of the motor 23 until the evaporator core temperature is stabilised at the desired 3° C.-5° C. temperature.

If the heat load on the evaporator is increased, the evaporator core temperature will also increase. If the evaporator core temperature is above 3° C.-5° C., the controller 22 incrementally increases the speed of the motor 23 until the evaporator core temperature is stabilised at the desired 3° C.-5° C. temperature.

If the heat load on the evaporator is too high, the controller 22 causes the motor 23 to operate at its maximum speed of 2,200 rpm until the heat load on the evaporator has been sufficiently reduced. Once the heat load has been sufficiently reduced and the controller 22 has detected the decrease in evaporator core temperature from the sensor 21, the controller 22 decreases the speed of the motor 23 so as to thereby reduce the amount of electrical powered consumed by the air conditioner 20.

The evaporator of the air conditioner 20 is visible in FIGS. 2-5 and has been referenced with the numeral 32. The evaporator 32 includes a core 33 which has a plurality of parallel tubes. A compressed refrigerant gas flows through all of the tubes of the core 33 in the same direction. The refrigerant gas which flows through the evaporator 32 is 134 A gas which is the industry standard gas for automotive air conditioners. The core 33 also includes a plurality of fins which surround the tubes and which enable air to flow through the core 33 and past the tubes. The fins effectively increase the surface area of the core 33 which is able to come into contact with the air which flows through the core 33. As the refrigerant gas flows through the tubes and the air flows past the fins, heat is transferred between the refrigerant gas and the air. If the refrigerant gas is cooler than the air which flows past the fins, heat is transferred from the air to the refrigerant gas so that the air is thereby cooled.

The core 33 is a one-piece core which allows for the fins of the core 33 to have a temperature which is 4° C.-5° C. lower than that of a conventional tube and fin evaporator which is used in prior art air conditioners such as marine air conditioners.

The evaporator 32 is a 1.5 tonne/18,000 BTU evaporator. The air conditioner 20 is able to achieve longer cycling periods as a result of the accumulative capacity of the evaporator 32. This assists in reducing the amount of electrical power which is consumed by the motor 23.

The evaporator core 33 is mounted inside a housing 34 which is fabricated from a material such fibreglass or plastic which is non-conductive to prevent or inhibit corrosion and temperature losses. Ambient air is drawn through the evaporator core 33 by a barrel-type fan 35 which is of plastic construction and which is driven by a 90 W-130 W pancake type DC radial type electric motor. The motor delivers 360 CFM which equates to an output of 12,000 BTU. The air which passes through the evaporator 32 is output from a vent 36.

The refrigerant gas flows through a thermal expansion valve 37 of the air conditioner 20. Valve 37 is a changeable orifice thermal expansion valve which is manufactured by Danfoss®. The valve 37 has a number 6 orifice which gives the valve 37 a capacity of approximately 4 kW. This maximizes efficiencies through the evaporator 32.

Referring to FIGS. 4-6, the controller 22 is an electronic controller which is mounted on top of the electric motor 23 and which includes a circuit board 38, heat sinks 39, a cover 40, and a cooling fan 41. The controller 22 has three electronically controlled three phase outputs which are each connected to a respective phase of the motor 23. Position sensors, which are located at the back of the motor, output electric pulses to the controller 22 to indicate the position of armature. The controller 22 uses the pulses to determine the position of the armature. This enables the controller 22 to activate the phase outputs in a manner which causes the armature to rotate. It also allows for soft starting and soft stopping of the motor 23. Soft starting and soft stopping of the motor controls prevents electrical spikes in the electrical system of the air conditioner 20 which includes the battery 30 and other components which are connected to the battery 30.

The controller 22 has a 12V-48V DC input which is connected to the terminals of the battery 30 so that the battery 30 can supply electrical power to the controller 22. In addition, the controller 22 has a start/stop input for receiving an input signal which causes the controller 22 to start and stop the motor 23.

A second stage of the controller 22 has an evaporator feedback system which allows the motor 23 to reach a maximum speed of 2,200 rpm so that the evaporator 32 will then start to be cooled to a set temperature of 3° C. The signal which is output to the controller 22 by the temperature sensor 21 which measures the temperature of the evaporator core 33 causes the controller 22 to slow the motor 23 and therefore the compressor 26 so that the temperature of the evaporator core 33 is held at 3° C. As the temperature of the evaporator core 33 rises, the signal output by the temperature sensor 21 to the controller 22 causes the controller 22 to increase the speed of the motor 23 and therefore the compressor 26 so that the temperature of the evaporator core 33 is returned to 3° C.

The electric motor 23 is a brushless permanent magnet motor which has an aluminium housing and which is capable of producing up to 1 hp or 750 W. When the motor 23 is operating, the drive shaft 24 of the motor 23 rotates in a clockwise direction. The motor 23 has a soft start and soft stop capability, and, due to its brushless configuration, the motor 23 has no moving parts other than a respective sealed bearing at each end of its housing, and the drive shaft 24. The soft start and soft stop capability of the motor 23 prevents high surge currents in the motor 23 at start up, and harsh stop currents which can occur when power to an electric motor is abruptly disconnected. As mentioned previously, the drive shaft 24 is coupled to the drive shaft 27 of the compressor 26 so that the motor 23 is able to drive the compressor 26. The position sensors are housed in the rear of the motor 23.

The magnetic fields in the electric motor 23 are situated around the armature of the motor 23 and on the inside of the aluminium housing of the motor 23. This provides for better transfer of heat to the aluminium housing which functions as a heat sink.

The armature of the motor 23 employs skewed-type magnets which are configured to prevent the motor 23 from cogging. Cogging is a technical term which is used to describe the growling noise which conventional electric motors sometimes make when starting or when running at a low speed.

Although the motor 23 may operate from any suitable supply voltage, it is preferred that the motor 23 is of a type which operates from a 12V-48V supply voltage.

As mentioned previously, the compressor 26 is a scroll compressor of the type which is commonly used in automotive air-conditioning applications. Scroll compressors are manufactured by Sanden® and Nippodenso®. The compressor 26 of the air conditioner 20 depicted in FIGS. 2-5 is actually a modified scroll compressor which has had its standard electromagnetic drive system removed and replaced with the toothed pulley drive system of the air conditioner 20 which allows for non-slip drive. The non-slip drive of the air conditioner 20 reduces the amount of electrical current which is drawn by the electrical system of the air conditioner 20 by 2.5 A when the air conditioner 20 is supplied by a 12V DC voltage.

With reference to FIGS. 4, 5 and 7, the toothed pulley drive system of the air conditioner 20 includes the toothed pulley 25 which is mounted on the drive shaft 24 of the motor 23, and the toothed pulley 28 which is mounted on the drive shaft 27 of the compressor 26. The toothed pulleys 25, 28 are fabricated from aluminium, and the drive ratio of pulley 25 and pulley 28 is 3:1. The toothed pulley drive system also includes a toothed drive belt 42 which is referred to as a colt belt. The teeth of the drive belt 42 mesh with the teeth of the pulleys 25, 28 so as to inhibit the loss of power or torque when starting or stopping the motor 23. The drive belt 42 is 25 mm wide and has a circumference of 245 mm.

Referring to FIGS. 2-5 and 8, the air conditioner 20 also has a heat exchanger 43 which uses seawater to cool the refrigerant gas. It has been found that the use of seawater to cool the refrigerant gas increases the efficiency of the heat exchanger 43. The heat exchanger 43 is fabricated from stainless steel, copper and nickel, and has multiple bends in its interior so that the interior of the heat exchanger 43 resembles a tube and fin condenser core.

Seawater is pumped at a controlled rate through the heat exchanger 43 such that the seawater flows in the opposite direction to the flow of the refrigerant gas through the heat exchanger 43. In particular, a low wattage water pump circulates the seawater through the heat exchanger 43 at a rate of 13.3 L per minute. The water pump circulates the seawater through the heat exchanger 43 while the electric motor 23 drives the compressor 26.

The water pump is a Davies Craig™ 9002 brushless magnetic drive seal-less pump which has a 19 mm inlet and a 19 mm outlet, and which has a maximum pump rate of 13.3 L per minute. The water pump needs to be mounted below the waterline of the boat on which the air conditioner 20 is installed because the pump is not a self-priming pump. The water pump operates on a 12V input voltage, and uses only 1.5 A of electrical current. One of the reasons why the pump was selected was because the manufacturer indicates that the pump has an expected operating life of 15,000 hours.

The water circuit of the air conditioner 20 which includes the heat exchanger 43 also includes a scoop fitting which is located on the underside of the hull of the boat so that seawater is able to enter the water circuit through the scoop. After entering the water circuit, the seawater passes through a seawater strainer which prevents foreign matter from entering the water pump. The strained seawater then flows into the inlet of the water pump and is then pumped out of the outlet of the water pump and through the heat exchanger 43. The seawater which is pumped through the heat exchanger 43 is then discharged from the boat. The heat exchanger 43 is fitted above the waterline of the hull so that it can be readily determined whether seawater is being pumped through the heat exchanger 43.

The interface module 29 includes a panel which allows for the input of signals to and the output of signals from the air conditioner 20. The interface module 29 monitors the terminal voltage of the battery 30 to ensure that the terminal voltage does not drop below 10.5V if the air conditioner 20 requires a 12V DC supply voltage. If the terminal voltage decreases to 10.5V, the air conditioner 20 shuts down until such time that the battery 30 has been recharged to at least 12.5V.

The interface module 29 includes a 12V or 24V power supply for the water pump which pumps seawater through the heat exchanger 43. The interface module 29 also has a system which provides a safety shutdown which prevents overheating of the essential components of the air conditioner 20. There is a switch on the high-pressure side of the refrigerant gas circuit which, once the pressure in that part of the refrigerant gas circuit reaches 150 psi as a consequence of, for example, a blockage in the water circuit which includes the heat exchanger 43, the latching relay will trip so that all electrical power is cut off from the electrical system of the air conditioner 20 so as to prevent damage to the air conditioner 20. There is also a similar system on the low-pressure side of the compressor 26 that will trip in order to prevent the compressor 26 from being damaged if the gas pressure on that side of the compressor 26 falls below 30 psi.

The interface module 29 has outputs a buzzer signal to the user control panel 31 if the high pressure switch is activated. When this occurs, the air conditioner 20 cannot be restarted until after the electrical power to the air conditioner 20 has been switched off at the user control panel 31. Once the fault is rectified, the power switch on the user control panel 31 is returned to the on position so that the air conditioner 20 can recommence operating.

The speed of the evaporator fan is adjustable. The air conditioner 20 also has overload protection, short circuit protection and three inputs for the control panel 31.

Referring to FIG. 9, the user control panel 31 is connected to the interface module 29 by a wiring loom. This allows the control panel 31 to be mounted at a convenient location on the boat.

The control panel 31 has a room temperature setting display 44 which displays the desired room temperature. The control panel 31 also has two buttons 45 which, if pressed simultaneously, can be used to adjust the displayed desired room temperature. If the desired room temperature is adjusted, the air conditioner 20 adjusts the actual room temperature to the desired room temperature as displayed by the display 44. The air conditioner 20 has a temperature sensor which is in the form of a thermistor and which senses the temperature of the air which is returned to the air conditioner 20. The air conditioner 20 turns off once the temperature of the return air reaches the desired room temperature. The air conditioner 20 operates in a cyclical manner in order to maintain the room temperature at the desired temperature. This is similar to the manner in which a household refrigerator operates. The air conditioner 20 users a 1° C. differential which means that, if, for example, the actual room temperature rises by 1° C., the compressor 26 is restarted so that the air conditioner 20 lowers the actual room temperature back to the desired room temperature.

The user control panel 31 also has a three-speed fan control knob 46 for adjusting the speed of the fan 35 which blows the cooled air from the vent 36. A user can select a slow, medium or fast fan speed by turning the knob 46 to the appropriate position.

The user control panel 31 also has a digital battery voltage indicator 47 which enables a user to visually monitor the terminal voltage level of the battery 30 so that they can determine whether the battery 30 needs to be recharged.

The air conditioner 20 also has a manual mechanical control panel.

The control panel has a cool/warm switch to enable reverse cycling. This is a valve that reverses the flow of refrigerant to heat the room air.

If the air conditioner 20 uses a 12V battery 30, it is preferred that a 50 A DC circuit breaker connects the interface module 29 to the positive terminal of the battery 30. The circuit breaker is preferably mounted externally on a DC distribution board which has a 50 A electrical current rating. It is preferred that 10 mm or larger electrical cabling is used in the air conditioner 20. This requires a positive and negative connection going into an Anderson plug®, which is a 50 A rating continuous connector.

The looms which are used in the air conditioner 20 are a two plug connector for the seawater pump, and an eight wire loom which connects the user control panel 31 to the interface module 29. The cables in the looming which connect the user control panel 31 to the interface module 29 may have RJ45 style plugs.

The air conditioner 20 is preferably bonded to the negative side of the boat's power supply to prevent any electrolysis from occurring.

The seawater pump preferably uses two 19 mm output and input hoses.

There is preferably a condensation discharge pipe which extends from a water collector at the bottom of the evaporator 32. Condensation occurs in the evaporator 32 as a result of moisture being collected from the air which is drawn through the evaporator 32. The water which is collected in the water collector of the evaporator is preferably drained out of the water collector through a half inch hose either by a collector sump and pumped out, or discharged out via a skin fitting.

The battery 30 is preferably a 12V absorbed glass mat battery. The required Ampere hours of the battery 30 are determined by the user requirements for the air conditioner 20.

The air conditioner 20 has reverse polarity protection which prevents the controller 22 and other components of the air conditioner 20 from being damaged in the event that the battery 30 is incorrectly installed.

The air conditioner 20 depicted in FIGS. 1-9 uses a 10.5-15V input voltage and an input current of 36-47 A. The air conditioner 20 consumes 430-564 W depending on the temperature of the seawater which is pumped through the heat exchanger 43, and the heat load of the air conditioner 20.

The air conditioner 20 has a length of 425 mm, a width of 450 mm, and a height of 320 mm. The weight of the air conditioner 20 is 29 kg.

The maximum noise level produced by the air conditioner 20 is 60 dB.

Throughout the specification and the claims, unless the context requires otherwise, the term “comprise”, or variations such as “comprises” or “comprising”, will be understood to apply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers.

Throughout the specification and claims, unless the context requires otherwise, the term “substantially” or “about” will be understood to not be limited to the value for the range qualified by the terms.

It will be appreciated by those skilled in the art that variations and modifications to the invention described herein will be apparent without departing from the spirit and scope thereof. The variations and modifications as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth.

It will be clearly understood that, if a prior art publication is referred to herein, that reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. 

1. An air conditioner comprising an evaporator for transferring heat from air to a refrigerant gas, a temperature sensor for sensing a temperature associated with the evaporator, a compressor for compressing the refrigerant gas, an electric motor for driving the compressor, and a controller for controlling the speed of the motor, wherein the controller is responsive to the temperature sensor.
 2. The air conditioner of claim 1, wherein the compressor is a scroll compressor.
 3. The air conditioner of claim 1, wherein the electric motor is a brushless DC motor.
 4. The air conditioner of claim 1, wherein the electric motor is adapted for soft starting and soft stopping.
 5. The air conditioner of claim 1, wherein the electric motor has multiple phases.
 6. The air conditioner of claim 5, wherein the air conditioner also comprises at least one position sensor for sensing the position of an armature of the motor.
 7. The air conditioner of claim 6, wherein the controller comprises a plurality of phase outputs, wherein each phase output is connected to a respective phase of the motor and is activated by the controller in response to the at least one position sensor.
 8. The air conditioner of claim 1, wherein the electric motor is a permanent magnet electric motor.
 9. The air conditioner of claim 8, wherein the armature of the electric motor comprises skewed-type magnets which are configured to prevent the motor from cogging.
 10. The air conditioner of claim 1, wherein the air conditioner also comprises a toothed pulley mounted on a drive shaft of the electric motor, a toothed pulley mounted on a drive shaft of the compressor, and a toothed drive belt trained around the pulleys such that the teeth of the drive belt mesh with the teeth of the pulleys.
 11. The air conditioner of claim 1, wherein the controller controls the speed of the motor to maintain the temperature of the evaporator at a predefined temperature or within a predefined range of temperatures.
 12. The air conditioner of claim 11, wherein the controller incrementally increases or decreases the speed of the motor if the temperature of the evaporator is not equal to the predefined temperature or does not fall within the predefined range of temperatures.
 13. The air conditioner of claim 11, wherein the controller increases the speed of the electric motor to a maximum speed if the heat load on the evaporator is too high, and then decreases the speed of the motor if the heat load on the evaporator decreases by a sufficient amount.
 14. The air conditioner of claim 1, wherein the controller also comprises a temperature sensor for sensing the temperature of the room or other space which is cooled by the air conditioner.
 15. The air conditioner of claim 14, wherein the air conditioner turns off when the temperature in the space reaches a predetermined room temperature, and turns on when the temperature in the space exceeds the predetermined room temperature by a minimum amount.
 16. The air conditioner of claim 1, wherein the air conditioner also comprises a user control panel for allowing a user to control the air conditioner.
 17. The air conditioner of claim 1, wherein the air conditioner also comprises an interface module for interfacing a DC power source with the controller.
 18. The air conditioner of claim 1, wherein the air conditioner also comprises a thermal expansion valve for the refrigerant gas.
 19. The air conditioner of claim 1, wherein the air conditioner also comprises a heat exchanger for cooling the refrigerant gas. 